Gaseous electric discharge lamp



April 1939- L. B. JOHNSON 2,152,997

GASEOUS ELECTRIC mscmmes LAMP Filed May 21, 1937 Fig.

'INVENTOR Lu man B. Johnson TTORNEY Patented 4, 1939- Gaseous nm'crmc DISCHARGE LAMP Lyman B. Johnson, East Orange, N. L, assignor to General. Electric Vapor-LampCompany, H boken, N. 1., a corporation of New Jersey Application May 21, 1937, Serial No. 144,070

2 Claims. (Cl. 176 122) The present invention relates to electric gaseous discharge lamps generally, and especially to lamps designed for use in optical systems and the like. I

5 A particular object of the invention is to produce a lamp of the electric gaseous discharge type which will have a uniform light distribution in all directions about its axisr A further object of the invention is to provide a tubular lamp of the single base type which will have this uniform, I light distribution characteristic; Still other objects and advantages of the invention will appear from the following-detailed, specification or from an inspection of the accompanying drawing. The invention consists in the new and novel structure and combination of elements, as hereinafter set forth and claimed.

Where lamps are used in connection with optical systems and the like it is frequently desirable that the light emission'therefrom should be uniform in all directions. This fact has created difliculties where lamps of the gaseous discharge type were used, due to the fact that these lamps generally involve the use of an elongated are path, with the necessity of making electrical connection to the electrodes at each end thereof.

Thus wherever a straight tube with a base attached to a single end thereof is employed it is necessary to bring one of the electrical leads 'back along the length of the envelope to this base. This lead obviously obstructs the light from the lamp, and while this obstruction is so small in amount as to be of no practical importance for general lighting purposes, it is sufllcient to produce objectionable asymmetry in the light provided for use in optical systems, such as those used for projection, for example, especially where. the light source is of high intrinsic brightness.

hence is no longer a source of asymmetry, a per-- fectly uniformly lighted field being obtainable 50 with-the inlead disposed in this novel manner about the discharge path.

For the purpose, of illustrating my invention I have shown a preferred embodiment thereof in the accompanying drawing in which 15 Fig. 1 is an elevational view of an electric gaseous discharge lamp of the high intrinsic brilliancy type which is now on the market, with its lead structure modified in accordance with my invention, and

Fig. 2 is a sectional view of the same lamp taken 5 I on the line 2-2 of Fig. 1..

As shown in these figures my novel lamp has a sealed envelope l of glass or the like to which a conventional base 2 is attached in the usual manner at the lower end. This envelope is prei- 1o erably clear in order not to lose the optical ad vantage o'fthe concentrated high intrinsic brilliancy Llight'lsoufice which is housed therein; Through thereentrant pinch seal 3 of said envelope there extend a pair of inleads t and 5 15 which are connected externally to said envelope with the tip and sleeve of the base 2 in a usual manner. Centrally disposed within said envelope I is a tubular capillary lamp, of a type which is now well known, having a {quartz envelope 6 20' into opposite ends of which are sealed inleads l and 8 through long beaded seals. These in- ;leads terminate within suitable electrode chambers at each end of said envelope 6, where they support activated thermionic cathodes 9' of the 25 self-heating type. The envelope 6.. contains. a suitable filling, as of argon and mercury,but since the details of the structure of this lamp form no part of the present invention they will not be further discussed here. The inlead 4 30 extends up past the lower seal of the envelope 6 and has a metal strip Ill welded thereto which passes around the beaded 'seal and thus affords support for said envelope 6. Electrical connection between said inlead 4 and the inlead 8 is 35 provided by means of a flexible stranded conductor H. The other inlead 5 extends upwardly to a point opposite the lower cathode 9, where it has welded thereto a metal strip l2 which encircles the adjacent electrode chamber of the 40 envelope 6, thus affording further support for said envelope and also providing an external electrode which materially decreases the voltage required to initiate a discharge between the electrodes 9. A helix l3 of say 20 mil wire, of tungsten, molybdenum, nickel or other suitable metal has one end welded to the inlead 5 near the end thereof and extends along the envelope 6 and light emitting portion of the envelope 6, between the electrodes s, so that the light obstruction by said helix will be identical. in every direction about the axis of the lamp. Electrical connection is established between the helix it and the inlead 1 by means of the short flexible conductor it oi stranded wire.

Upon connection of this lamp to a suitable source of electrical energy through the customary ballasting impedance a discharge is initiated be tween the cathodes d which is highly constricted and of extremely high intrinsic brilliancy. l'he light from this discharge is very effective, due to this high brilliancy and the relatively small area of the source, for use with optical systems, especially in view of the novel use of the low resist ance helical lead it, whereby the production oi. asymmetrical shadows is avoided, and uniform illumination of all pointsabout the axis obtained.

While I have described my invention by refer ence to a specific embodiment thereof, it is to be understood that it is not limited thereto, but that arsaaov various changes, omissions and substitutions, within the scope of the appended claims, may be made therein without departing from the spirit of the invention.

taining a gaseous atmosphere and having eleo- Y trodes sealed therein adjacent opposite ends thereof with a constricted arc path between said electrodes to provide a light source of high in-- trinsic brilliancy, a supporting base adjacent one end of said envelope and having a pair of leads, one of said leads being connected to the adjacent electrode of said lamp while the other of said leads extends helically about said envelope without light obstructing supports to a point beyond the discharge path, and with a whole number of turns opposite said discharge path, to make a connection with the other electrode, whereby the shadow cast by the latter lead is symmetrical about the axis of said envelope.

2. An electric lamp comprising a sealed envelope, means to conduct an electrical current along a line path between two terminals therein to produce light radiations, and a pair of electrical leads to said terminals, one of said leads extending in the shape of a coaxial helix about said line path with a plurality of whole turns interposed between said terminals, whereby the light distribution from. said line path is substan tially uniform in all directions.

LYMAN Bu JOHNSON Eli 

